Secondary battery

ABSTRACT

An exemplary embodiment provides a lithium ion secondary battery using a high energy type anode, which enables long-life operation thereof. A secondary battery according to an exemplary embodiment comprises an electrode element in which a cathode and an anode are oppositely disposed, an electrolytic solution, and an outer packaging body which encloses the electrode element and the electrolytic solution inside; wherein the anode is formed by binding an anode active material, which comprises carbon material (a) that can absorb and desorb a lithium ion, metal (b) that can be alloyed with lithium, and metal oxide (c) that can absorb and desorb a lithium ion, to an anode collector with an anode binder; and wherein the electrolytic solution comprises a liquid medium which is hard to generate carbon dioxide at a concentration of 10 to 75 vol %.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2010/066915 filed Sep. 29, 2010, claiming priorities basedJapanese Patent Application Nos. 2009-224546, filed Sep. 29, 2009 and2010-196630, filed Sep. 2, 2010 the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

An exemplary aspect of the invention relates to a secondary battery, andparticularly to a lithium ion secondary battery.

BACKGROUND ART

With rapid market expansion of laptop computers, mobile phones, electricvehicles, and the like, a secondary battery having a high energy densityis required. Examples of a method for obtaining a secondary batteryhaving a high energy density include a method in which an anode materialhaving large capacity is used, and a method in which a nonaqueouselectrolytic solution having a superior stability is used.

Patent document 1 discloses using silicon oxide or a silicate as ananode active material of a secondary battery. Patent document 2discloses an anode for a secondary battery which has an active materiallayer containing a particle of carbon material that can absorb anddesorb a lithium ion, a metal particle that can be alloyed with lithium,and an oxide particle that can absorb and desorb a lithium ion. Patentdocuments 3 discloses an anode material for a secondary battery which isformed by coating a surface of a particle, which has a structure inwhich silicon fine crystal is dispersed in a silicon compound, withcarbon.

Patent document 4 discloses using a fluorinated chain ether compoundwhich has a superior stability and which, for example, has the followingstructure as a nonaqueous electrolytic solution:

Patent document 5 and Patent document 6 disclose using a polyimide as ananode binder when an anode active material contains silicon. Patentdocument 7 discloses using a polyamide-imide as an anode binder.

PRIOR ART DOCUMENT Patent Document

Patent document 1: JP 06-325765 A

Patent document 2: JP 2003-123740 A

Patent document 3: JP 2004-47404 A

Patent document 4: JP 11-26015 A

Patent document 5: JP 2004-22433 A

Patent document 6: JP 2007-95670 A

Patent document 7: JP 2002-190297 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, when charging and discharging are carried out at 45° C. orhigher in the case where the silicon oxide described in Patent document1 is used as an anode active material, there has been a problem in whichcapacity deterioration associated with a charge/discharge cycle issignificantly large. The anode for a secondary battery described inPatent document 2 has an effect in which volume change of the anode as awhole is relaxed due to the different charge/discharge electricpotentials among three kinds of components when a lithium ion isabsorbed and desorbed. However, in Patent document 2, there have beenmany points which are not sufficiently studied, such as a pointregarding a relationship among three kinds of components in a state ofcoexistence, and points regarding a binder, an electrolytic solution, anelectrode element structure, and an outer packaging body which areindispensable for a formation of a lithium ion secondary battery. Theanode material for a secondary battery described in Patent document 3also has an effect in which volume expansion of the anode as a whole isrelaxed. However, in Patent document 3, there have been many pointswhich are not sufficiently studied, such as points regarding a binder,an electrolytic solution, an electrode element structure, and an outerpackaging body which are indispensable for a formation of a lithium ionsecondary battery.

The nonaqueous electrolytic solution described in Patent document 4 isused to utilize noncombustibility or oxidation resistivity thereof, buthas never been used to effectively suppress generation of carbon dioxidewhich is associated with reductive decomposition of a nonaqueouselectrolytic solution. Also, in Patent document 4, there have been manypoints which are not sufficiently studied, such as points regarding ananode active material, an electrode element structure, and an outerpackaging body which are indispensable for a formation of a lithium ionsecondary battery.

In Patent documents 5 to 7, a study regarding a state of an anode activematerial is insufficient, and additionally there have been many pointswhich are not sufficiently studied, such as points regarding an anodeactive material, an electrode element structure, and an outer packagingbody which are indispensable for a formation of a lithium ion secondarybattery.

Thus, an exemplary aspect of the invention is intended to provide alithium ion secondary battery using a high energy type anode, whichenables long-life operation thereof.

Means for Solving the Problem

An exemplary aspect of the invention is a secondary battery, comprisingan electrode element in which a cathode and an anode are oppositelydisposed, an electrolytic solution, and an outer packaging body whichencloses the electrode element and the electrolytic solution inside;

wherein the anode is formed by binding an anode active material, whichcomprises carbon material (a) that can absorb and desorb a lithium ion,metal (b) that can be alloyed with lithium, and metal oxide (c) that canabsorb and desorb a lithium ion, to an anode collector with an anodebinder; and

wherein the electrolytic solution comprises a liquid medium which ishard to generate carbon dioxide at a concentration of 10 to 75 vol %.

Effect of the Invention

According to an exemplary aspect of the invention, a lithium ionsecondary battery using a high energy type anode, which enableslong-life operation thereof, can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view showing a structure of an electrodeelement in a stacked laminate type secondary battery.

MODE FOR CARRYING OUT THE INVENTION

As follows, an exemplary embodiment of the invention is described indetail.

In a secondary battery according to an exemplary embodiment of theinvention, an electrode element in which a cathode and an anode areoppositely disposed and an electrolytic solution are enclosed inside anouter packaging body. As for the shape of the secondary battery,cylindrical type, flattened spiral square type, stacked square type,coin type, flattened spiral laminate type, and stacked laminate type canbe used, but stacked laminate type is preferable. As follows, a stackedlaminate type secondary battery is described.

FIG. 1 is a schematic sectional view showing a structure of an electrodeelement in a stacked laminate type secondary battery. This electrodeelement is formed by alternately stacking a plurality of cathodes c anda plurality of anodes a with separators b placed therebetween. Cathodecollectors e in each cathodes c are electrically connected by beingwelded one another at the end parts thereof which are not covered with acathode active material, and further a cathode terminal f is welded tothe welded part. Anode collectors d in each anodes a are electricallyconnected by being welded one another at the end parts thereof which arenot covered with an anode active material, and further an anode terminalg is welded to the welded part.

There is an advantage in the electrode element having such a planarstacking structure such that it is hardly affected by volume change ofthe electrode which is associated with charging and discharging, incomparison with the electrode element having a spiral structure becausethere is no part having small R (such as area near spiral center of thespiral structure). That is, the electrode element is useful when anactive material which easily generates volume expansion is used. On theother hand, the electrode is bent in the electrode element having aspiral structure, which results in distortion of the structure due togeneration of volume change. In particular, in the case of using ananode active material such as a silicon oxide which generates largevolume change associated with charging and discharging, large capacitydeterioration which is associated with charging and discharging occursin a secondary battery using an electrode element having a spiralstructure.

However, the electrode element having a planar stacking structure has aproblem that a gas which is generated between the electrodes easilyaccumulates between the electrodes. This is because, in the case of theelectrode element having a stacking structure, it is easy to extend thespace between the electrodes, while, in the case of the electrodeelement having a spiral structure, the electrodes are tensionedtherebetween and thereby the space between the electrodes is hard to beextended. In the case where the outer packaging body is an aluminumlamination film, this problem becomes particularly significant.

An exemplary embodiment of the invention can solve the above-mentionedproblem, and can provide a lithium ion secondary battery using a highenergy type anode, which enables long-life operation thereof.

[1] Anode

An anode is formed by binding an anode active material on an anodecollector with an anode binder so that the anode active material coversthe anode collector. In an exemplary embodiment of the invention, carbonmaterial (a) that can absorb and desorb a lithium ion, metal (b) thatcan be alloyed with lithium, and metal oxide (c) that can absorb anddesorb a lithium ion are used.

As carbon material (a), graphite, amorphous carbon, diamond-like carbon,carbon nanotube or a complex thereof may be used. Here, graphite whichhas high crystallinity has a high electroconductivity and has a superioradhesiveness with a cathode collector made of copper or the like as wellas a superior voltage flatness. On the other hand, amorphous carbonwhich has low crystallinity has a relatively low volume expansion.Therefore, there is a high effect of relaxing volume expansion anddeterioration due to ununiformity such as crystal grain boundary ordefect is hard to occur.

As metal (b), Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, Laor an alloy of two or more kinds thereof can be used. Particularly, itis preferable to contain silicon (Si) as metal (b).

As metal oxide (c), silicon oxide, aluminum oxide, tin oxide, indiumoxide, zinc oxide, lithium oxide or a complex thereof can be used.Particularly, it is preferable to contain silicon oxide as metal oxide(c). This is because silicon oxide is relatively stable and is hard tocause a reaction with another chemical compound. Also, metal oxide (c)is preferably an oxide of a metal which constitutes metal (b). Also, onekind or two or more kinds of element selected from nitrogen, boron andsulfur can be added to metal oxide (c), for example, in an amount of 0.1to 5 mass %. In this way, electroconductivity of metal oxide (c) can beimproved.

As for metal oxide (c), all or a part thereof preferably has anamorphous structure. Metal oxide (c) having an amorphous structure cansuppress volume expansion of carbon material (a) or metal (b) that isanother anode active material and can also suppress decomposition of anelectrolytic solution containing a fluorinated ether compound. Thismechanism is not obvious, but the amorphous structure of metal oxide (c)is presumed to have some influence on a formation of coating at aninterface between carbon material (a) and an electrolytic solution.Also, the amorphous structure has relatively small amount of influencedue to ununiformity such as crystal grain boundary or defect. Note that,it can be confirmed by X-ray diffraction measurement (common XRDmeasurement) that all or a part of metal oxide (c) has an amorphousstructure. Specifically, in the case where metal oxide (c) does not havean amorphous structure, a peak peculiar to metal oxide (c) is observed,while in the case where all or a part of metal oxide (c) has anamorphous structure, a peak peculiar to metal oxide (c) that is observedcomes to be broad.

Also, as for metal (b), all or a part thereof is preferably dispersed inmetal oxide (c). Dispersing at least a part of metal (b) in metal oxide(c) can suppress volume expansion of the anode as a whole and can alsosuppress decomposition of an electrolytic solution. Note that, it can beconformed by transmission electron microscope observation (general TEMobservation) in combination with energy dispersive X-ray spectroscopymeasurement (general EDX measurement) that all or a part of metal (b) isdispersed in metal oxide (c). Specifically, a section of a specimen ofmetal particle (b) is observed and an oxygen atom concentration of metalparticle (b) which is dispersing in metal oxide (c) is measured, andthereby it can be confirmed that a metal which constitutes metalparticle (b) does not become an oxide.

An anode active material containing carbon material (a), metal (b) andmetal oxide (c), in which all or a part of metal oxide (c) has anamorphous structure and in which all or a part of metal (b) is dispersedin metal oxide (c), can be produced for example by a method disclosed inPatent document 3. That is, CVD processing of metal oxide (c) isperformed under an atmosphere containing an organic substance gas suchas methane gas, to obtain a complex in which metal (b) in metal oxide(c) is a nanocluster, and in which the surface is covered with carbonmaterial (a). Also, the above-mentioned anode active material is alsoproduced by mixing carbon material (a), metal (b) and metal oxide (c) bymechanical milling.

There is no limitation for the ratios of carbon material (a), metal (b)and metal oxide (c) in particular. The ratio of carbon material (a) ispreferably 2 mass % or more and 50 mass % or less with respect to thetotal amount of carbon material (a), metal (b) and metal oxide (c), andis preferably 2 mass % or more and 30 mass % or less. The ratio of metal(b) is preferably 5 mass % or more and 90 mass % or less with respect tothe total amount of carbon material (a), metal (b) and metal oxide (c),and is preferably 20 mass % or more and 50 mass % or less. The ratio ofmetal oxide (c) is preferably 5 mass % or more and 90 mass % or lesswith respect to the total amount of carbon material (a), metal (b) andmetal oxide (c), and is preferably 40 mass % or more and 70 mass % orless.

Also, each of carbon material (a), metal (b) and metal oxide (c) usedmay be, but should not be particularly limited to, a particle thereof.For example, the average particle diameter of metal (b) can beconstituted in a range smaller than the average particle diameter ofcarbon material (a) and the average particle diameter of metal oxide(c). From this constitution, since metal (b) in which volume changewhich is associated with charge and discharge is small has a relativelysmall particle diameter, and since carbon material (a) and metal oxide(c) in which volume change is large have a relatively large particlediameter, dendrite generation and pulverization of alloy are moreeffectively suppressed. Also, in the process of charge and discharge, alithium ion is absorbed and desorbed from the larger diameter particle,the smaller diameter particle and the larger diameter particle in thisorder. From this point, residual stress and residual strain aresuppressed. The average particle diameter of metal (b) is, for example,20 μm or less, and is preferably 15 μm or less.

Also, it is preferable that the average particle diameter of metal oxide(c) is a half or less of the average particle diameter of carbonmaterial (a), and it is preferable that the average particle diameter ofmetal (b) is a half or less of the average particle diameter of metaloxide (c). It is even more particularly preferable that the averageparticle diameter of metal oxide (c) is a half or less of the averageparticle diameter of carbon material (a) as well as that the averageparticle diameter of metal (b) is a half or less of the average particlediameter of metal oxide (c). Controlling the average particle diameterin this range can more effectively give a relaxation effect of thevolume expansion of metal and alloy phase, and can provide a secondarybattery having superior balance of energy density, cycle life andefficiency. More specifically, it is preferable that the averageparticle diameter of silicon oxide (c) is a half or less of the averageparticle diameter of graphite (a) and that the average particle diameterof silicon (b) is a half or less of the average particle diameter ofsilicon oxide (c). Also, more specifically, the average particlediameter of silicon (b) is, for example, 20 μm or less, and ispreferably 15 μm or less.

As an anode binder, a polyvinylidene fluoride, a vinylidenefluoride-hexafluoropropylene copolymer, a vinylidenefluoride-tetrafluoroethylene copolymer, a styrene-butadienecopolymerized rubber, a polytetrafluoroethylene, a polypropylene, apolyethylene, a polyimide, a polyamide-imide or the like may be used.Among them, from the viewpoint of strong binding property, a polyimideor a polyamide-imide is preferable. The amount of the anode binder usedis preferably 5 to 25 parts by mass with respect to 100 parts by mass ofthe anode active material from the viewpoint of “sufficient bindingforce” and “high energy” which are in trade-off relationship to eachother.

As an anode collector, aluminum, nickel, copper, silver and alloyingthereof are preferable from the viewpoint of electrochemical stability.Examples of the shape thereof include foil, flat plate and mesh.

An anode can be produced by forming an anode active material layercontaining an anode active material and an anode binder on an anodecollector. Examples of the method for forming the anode active materiallayer include doctor blade method, die coater method, CVD method, andsputtering method. An anode active material layer is first formed, and athin film of aluminum, nickel or an alloy thereof is thereafter formedby vapor deposition, sputtering or the like to form an anode collector.

[2] Cathode

A cathode is formed for example by binding a cathode active material ona cathode collector with a cathode binder so that the cathode activematerial covers the cathode collector.

Examples of the cathode active material include lithium manganateshaving a layered structure or lithium manganates having a Spinelstructure including LiMnO₂ and Li_(x)Mn₂O₄ (0<x<2); LiCoO₂, LiNiO₂ andmaterials in which a part of transition metal thereof are substitutedwith another metal; lithium transition metal oxides such asLiNi_(1/3)CO_(1/3)Mn_(1/3)O₂ in which the molar ratio of a particulartransition metal is not more than a half; and materials which havelithium at a larger amount than the stoichiometric amount in theselithium transition metal oxides. Particularly,Li_(α)Ni_(β)CO_(γ)Al_(δ)O₂ (1≦α≦1.2, β+γ+δ=1, β≧0.7, and γ≦0.2) orLi_(α)Ni_(β)CO_(γ)Mn_(δ)O₂ (1≦α≦1.2, β+γ+δ=1, β≧0.6, and γ≧0.2) ispreferable. The cathode active material may be used alone, or incombination with two or more kinds.

As a cathode binder, a material for a cathode binder or the like may beused. Among them, from the viewpoint of versatility and low cost, apolyvinylidene fluoride is preferable. The amount of the cathode binderused is preferably 2 to 10 parts by mass with respect to 100 parts bymass of the cathode active material, from the standpoint of “sufficientbinding force” and “high energy” which are trade-off to each other.

As a cathode collector, a material for an anode collector or the likecan be used.

For the purpose of reducing impedance, an electroconductive auxiliarymaterial may be added to a cathode active material layer containing acathode active material. Examples of the electroconductive auxiliarymaterial include carbonaceous fine particles such as graphite, carbonblack, and acetylene black.

[3] Electrolytic Solution

An electrolytic solution used in an exemplary embodiment of theinvention contains a liquid medium which is hard to generate carbondioxide at a concentration of 10 to 75 vol %. The concentration of theliquid medium which is hard to generate carbon dioxide in theelectrolytic solution is more preferably 15 to 70 vol %, and is furtherpreferably 15 to 60 vol %. Note that, the liquid medium which is hard togenerate carbon dioxide is definitely distinguished from liquid mediawhich generate carbon dioxide by a general combustion reaction and ischaracterized by being hard to generate carbon dioxide by electrolysis.Particularly, it is characterized by being hard to generate carbondioxide by reductive decomposition. Thus, it means a liquid medium suchas a liquid medium which does not have a carbonate group (−CO₃— group)or —COO— group in the molecular structure, which has a carbon atom inthe molecular structure and an oxygen atom double-bonded to a carbonatom, but which the molar ratio of the oxygen atom adjacent to thecarbon atom is not set to be 1:2 or more.

Examples of the liquid medium which is hard to generate carbon dioxideinclude chain ether compounds; cyclic ether compounds;dimethylsulfoxide, 1,3-dioxolane, formamide, acetamide,dimethylformamide, 1,2-dioxolane, acetonitrile, propionitrile,nitromethane, ethyl monoglyme, phosphoric acid triesters, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane,1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone,tetrahydrofuran derivatives, 1,3-propane sultone, anisole,N-methylpyrrolidone, ionic liquids, liquid phosphazenes. The liquidmedium which is hard to generate carbon dioxide can be used alone, or incombination with two or more kinds.

A chain ether compound may be a non-fluorinated chain ether compound ora fluorinated chain ether compound in which a part of hydrogen atoms ofa non-fluorinated chain ether compound are substituted by fluorineatom(s). Examples of the non-fluorinated chain ether compound includenon-fluorinated chain monoether compounds such as dimethyl ether, methylethyl ether, diethyl ether, methyl propyl ether, ethyl propyl ether,dipropyl ether, methyl butyl ether, ethyl butyl ether, propyl butylether, dibutyl ether, methyl pentyl ether, ethyl pentyl ether, propylpentyl ether, butyl pentyl ether, and dipentyl ether; andnon-fluorinated chain diether compounds such as 1,2-dimethoxyethane(DME), 1,2-diethoxyethane (DEE), ethoxymethoxyethane (EME),1,2-dipropoxy ethane, propoxyethoxyethane, propoxymethoxyethane,1,2-dibutoxyethane, butoxypropoxyethane, butoxyethoxyethane,butoxymethoxyethane, 1,2-dipentoxyethane, pentoxybutoxyethane,pentoxypropoxyethane, pentoxyethoxyethane, and pentoxymethoxyethane.

A cyclic ether compound may be a non-fluorinated cyclic ether compoundor a fluorinated cyclic ether compound in which a part of hydrogen atomsof a non-fluorinated cyclic ether compound are substituted by fluorineatom(s). Examples of the non-fluorinated cyclic ether compound includenon-fluorinated cyclic monoether compounds such as ethylene oxide,propylene oxide, oxetane, tetrahydrofuran, 2-methyltetrahydrofuran,3-methyltetrahydrofuran, tetrahydropyran, 2-methyltetrahydropyran,3-methyltetrahydropyran, and 4-methyl tetrahydropyran; andnon-fluorinated cyclic diether compounds such as 1,3-dioxolane,2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane,2-methyl-1,4-dioxane, 1,3-dioxane, 2-methyl-1,3-dioxane,4-methyl-1,3-dioxane, 5-methyl-1,3-dioxane, 2,4-dimethyl-1,3-dioxane,and 4-ethyl-1,3-dioxane.

A liquid medium which is hard to generate carbon dioxide preferably hasno —COO— group which is easy to generate carbon dioxide. Particularly, aliquid medium which is hard to generate carbon dioxide is morepreferably a chain ether compound which has a good compatibility withanother nonaqueous electrolytic solution, and is further preferably afluorinated chain ether compound which has a good stability. Thefluorinated chain ether compound is preferably a compound represented byfollowing formula (1):H—(CX¹X²—CX³X⁴)_(n)—CH₂O—CX⁵X⁶—CX⁷X⁸—H  (1).In formula (1), n is 1, 2, 3 or 4, and X¹ to X⁸ are each independently afluorine atom or a hydrogen atom. However, at least one of X¹ to X⁴ is afluorine atom, and at least one of X⁵ to X⁸ is a fluorine atom. Also, asfor the atom ratio of the fluorine atom and the hydrogen atom which arebonded to the compound of formula (1), [(the total number of thefluorine atom)/(the total number of the hydrogen atom)]≧1.It is more preferably following formula (2):H—(CF₂—CF₂)_(n)—CH₂O—CF₂—CF₂—H  (2).In formula (2), n is 1 or 2.

Note that, in one embodiment, the liquid medium which is hard togenerate carbon dioxide may be a medium which does not contain aphosphoric acid ester compound. Examples of the phosphoric acid estercompound include non-fluorinated phosphoric acid ester compounds andfluorinated phosphoric acid ester compounds.

A fluorinated phosphoric acid ester compound may be a compoundrepresented by following formula (A):

In formula (A), x, y and z are each independently 0, 1 or 2, and l, mand n are each independently an integer of 0 to 3, and a, b and c areeach independently an integer of 0 to 3. However, x×1, y×m, z×n, a, band c are not all together set to be 0.

It may also be a compound represented by following formula (B):O═P(OCH₂CF₃)₃  (B).Note that, 1 to 3 out of three ester structures in the above-mentionedfluorinated phosphoric acid ester compound may be a non-fluorinatedphenyl ester structure or a non-fluorinated phenyl ester structure.

A non-fluorinated phosphoric acid ester is preferably a compoundrepresented by following formula (C):

In formula (C), p, q and r are each independently an integer of 0 to 3.Note that, 1 to 3 out of three ester structures in the above-mentionednon-fluorinated phosphoric acid ester compound may be a non-fluorinatedphenyl ester structure.

An electrolytic solution used in an exemplary embodiment of theinvention contains a nonaqueous electrolytic solution which is stable atan electric potential of battery operation, along with a liquid mediumwhich is hard to generate carbon dioxide. Examples of the nonaqueouselectrolytic solution include non-protic organic solvents, for example,cyclic carbonates such as propylene carbonate (PC), ethylene carbonate(EC), butylene carbonate (BC), and vinylene carbonate (VC); chaincarbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC),ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC); propylenecarbonate derivatives; and aliphatic carboxylic acid esters such asmethyl formate, methyl acetate, and ethyl propionate. The nonaqueouselectrolytic solution is preferably a cyclic or chain carbonates such asethylene carbonate (EC), propylene carbonate (PC), butylene carbonate(BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethylcarbonate (DEC), ethyl methyl carbonate (MEC), or dipropyl carbonate(DPC). The nonaqueous electrolytic solution can be used alone, or incombination with two or more kinds.

An electrolytic solution used in an exemplary embodiment of theinvention is formed by adding a supporting salt to a mixed liquid of aliquid medium which is hard to generate carbon dioxide and a nonaqueouselectrolytic solution. Examples of the supporting salt include lithiumsalts such as LiPF₆, LiAsF₆, LiAlCl₄, LiClO₄, LiBF₄, LiSbF₆, LiCF₃SO₃,LiC₄F₉SO₃, Li(CF₃SO₂)₂, and LiN(CF₃SO₂)₂. The supporting salt can beused alone, or in combination with two or more kinds.

[4] Separator

As a separator, a porous film or a nonwoven cloth which is made ofpolypropylene or polyethylene can be used. A separator in which theseare stacked can also be used.

[5] Outer Packaging Body

An outer packaging body is arbitrarily selected as long as it is stableagainst an electrolytic solution and it has a water vapor barrierproperty. For example, in the case of a stacked laminate type secondarybattery, a lamination film of polypropylene; polyethylene, or the likewhich is coated with aluminum or silica is preferably used as an outerpackaging body. Particularly, it is preferable to use an aluminumlamination film from the viewpoint of suppression of volume expansion.

In the case of a secondary battery in which a lamination film is used asan outer packaging body, when a gas is generated, distortion of theelectrode element becomes much larger, than in the case of a secondarybattery in which a metal can is used as an outer packaging body. This isbecause the lamination film is easily deformed by the inner pressure ofthe secondary battery in comparison with the metal can. Furthermore, inthe case of the secondary battery in which a lamination film is used asan outer packaging body, the inner pressure of the battery is generallyset to be lower than atmospheric pressure when it is sealed. Thus, thebattery does not have extra space, which directly results in volumechange of the battery and deformation of the electrode element.

However, a secondary battery according to an exemplary embodiment of theinvention can overcome the above-mentioned problem. As a result, astacked laminate type lithium ion secondary battery which is cheap andwhich is superior in design flexibility of the cell capacity by changingthe number of lamination can be provided.

EXAMPLE

As follows, an exemplary embodiment of the invention is specificallydescribed by Examples.

Example 1

Graphite having an average particle diameter of 30 μm as carbon material(a), silicon having an average particle diameter of 5 μm as metal (b),and amorphous silicon oxide (SiO_(x), 0<x≦2) having an average particlediameter of 13 μm as metal oxide (c) silicon were weighed at a massratio of 5:35:60 and were mixed by so-called mechanical milling for 24hours to obtain an anode active material. Note that, in this anodeactive material, silicon that is metal (b) was dispersed in siliconoxide (SiO_(x), 0<x≦2) that is metal oxide (c).

The above-mentioned anode active material (average particle diameterD50=5 μm) and a polyimide (PI, produced by UBE INDUSTRIES, trade name: Uvarnish A) as an anode binder were weighed at a mass ratio of 90:10 andthey were mixed with n-methylpyrrolidone to form an anode slurry. Theanode slurry was applied on copper foil having a thickness of 10 μm andwas then dried, and it was further heat-treated under nitrogenatmosphere at 300° C. to produce an anode.

Lithium nickelate (LiNi_(0.80)CO_(0.15)Al_(0.15)O₂) as a cathode activematerial, carbon black as an electroconductive auxiliary material, and apolyvinylidene fluoride as a cathode binder were weighed at a mass ratioof 90:5:5 and they were mixed with n-methylpyrrolidone to form a cathodeslurry. The cathode slurry was applied on aluminum foil having athickness of 20 μm and was then dried, and it was further pressed toproduce an anode.

The three layers of the cathode obtained and the four layers of theanode obtained were alternately stacked with a polypropylene porous filmas a separator placed therebetween. End parts of the cathode collectorswhich were not covered with the cathode active material and of theanodes collectors which were not covered with the anode active materialwere respectively welded, and further an aluminum cathode terminal and anickel anode terminal were respectively welded thereto, to obtain anelectrode element which had a planar stacking structure.

On the other hand, a liquid medium which is hard to generate carbondioxide and a carbonate type nonaqueous electrolytic solution was mixedat 40:60 (volume ratio). H—CF₂CF₂—CH₂O—CF₂CF₂—H that is a fluorinatedchain ether compound was used as the liquid medium which is hard togenerate carbon dioxide, and a mixed solvent ofEC/PC/DMC/EMC/DEC=20/20/20/20/20 (volume ratio) which contained LiPF₆ at2 mol/l was used as the carbonate type nonaqueous electrolytic solution.The final concentration of LiPF₆ as a supporting salt was thereby set tobe 1.2 mol/l.

The above-mentioned electrode element was embedded in an aluminumlamination film as an outer packaging body and the nonaqueouselectrolytic solution was injected thereinto. After that, it wasdepressurized to 0.1 atm and was sealed to produce a secondary battery.

Example 2

This example was carried out in the same manner as in Example 1 exceptthat the mixing ratio of the liquid medium which is hard to generatecarbon dioxide to the carbonate type nonaqueous electrolytic solutionwas set to be 10:90 (volume ratio).

Example 3

This example was carried out in the same manner as in Example 1 exceptthat the mixing ratio of the liquid medium which is hard to generatecarbon dioxide to the carbonate type nonaqueous electrolytic solutionwas set to be 15:85 (volume ratio).

Example 4

This example was carried out in the same manner as in Example 1 exceptthat the mixing ratio of the liquid medium which is hard to generatecarbon dioxide to the carbonate type nonaqueous electrolytic solutionwas set to be 50:50 (volume ratio).

Example 5

This example was carried out in the same manner as in Example 1 exceptthat the mixing ratio of the liquid medium which is hard to generatecarbon dioxide to the carbonate type nonaqueous electrolytic solutionwas set to be 60:40 (volume ratio).

Example 6

This example was carried out in the same manner as in Example 1 exceptthat the mixing ratio of the liquid medium which is hard to generatecarbon dioxide to the carbonate type nonaqueous electrolytic solutionwas set to be 70:30 (volume ratio), and that a mixed solvent ofEC/PC/DMC/EMC/DEC=20/20/20/20/20 (a volume ratio) which contained LiPF₆at 2.4 mol/l was used as the carbonate type nonaqueous electrolyticsolution.

Example 7

This example was carried out in the same manner as in Example 1 exceptthat the mixing ratio of the liquid medium which is hard to generatecarbon dioxide to the carbonate type nonaqueous electrolytic solutionwas set to be 75:25 (volume ratio), and that a mixed solvent ofEC/PC/DMC/EMC/DEC=20/20/20/20/20 (a volume ratio) which contained LiPF₆at 2.4 mol/l was used as the carbonate type nonaqueous electrolyticsolution.

Comparative Example 1

This comparative example was carried out in the same manner as inExample 1 except that the liquid medium which is hard to generate carbondioxide was not used.

Comparative Example 2

This comparative example was carried out in the same manner as inExample 1 except that the mixing ratio of the liquid medium which ishard to generate carbon dioxide to the carbonate type nonaqueouselectrolytic solution was set to be 5:95 (volume ratio).

Comparative Example 3

This comparative example was carried out in the same manner as inExample 1 except that the mixing ratio of the liquid medium which ishard to generate carbon dioxide to the carbonate type nonaqueouselectrolytic solution was set to be 80:20 (volume ratio), and that amixed solvent of EC/PC/DMC/EMC/DEC=20/20/20/20/20 (volume ratio) whichcontained LiPF₆ at 2.4 mol/l was used as the carbonate type nonaqueouselectrolytic solution.

Example 8

This example was carried out in the same manner as in Example 1 exceptthat CH₂F—O—CH₂CH₃ that is a fluorinated chain ether compound was usedas the liquid medium which is hard to generate carbon dioxide.

Example 9

This example was carried out in the same manner as in Example 1 exceptthat CH₂F—O—CH₂CH₂F that is a fluorinated chain ether compound was usedas the liquid medium which is hard to generate carbon dioxide.

Example 10

This example was carried out in the same manner as in Example 1 exceptthat CH₂F—CH₂—O—CH₂CH₃ that is a fluorinated chain ether compound wasused as the liquid medium which is hard to generate carbon dioxide.

Example 11

This example was carried out in the same manner as in Example 1 exceptthat CH₂F—CH₂—O—CH₂CH₂F that is a fluorinated chain ether compound wasused as the liquid medium which is hard to generate carbon dioxide.

Example 12

This example was carried out in the same manner as in Example 1 exceptthat CH₂F—CH₂—O—CH₂CH₂—O—CH₂CH₃ that is a fluorinated chain ethercompound was used as the liquid medium which is hard to generate carbondioxide.

Example 13

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CF₂—CH₂O—CHFCF₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 14

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CF₂—CH₂O—CF₂CHF—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 15

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CF₂—CH₂O—CF₂CH₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 16

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CF₂—CH₂O—CH₂CH₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 17

This example was carried out in the same manner as in Example 1 exceptthat H—CHFCF₂—CH₂O—CF₂CF₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 18

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CHF—CH₂O—CF₂CF₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 19

This example was carried out in the same manner as in Example 1 exceptthat H—CH₂CF₂—CH₂O—CF₂CF₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 20

This example was carried out in the same manner as in Example 1 exceptthat H—CH₂CH₂—CH₂O—CF₂CF₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 21

This example was carried out in the same manner as in Example 1 exceptthat H—CHFCF₂—CH₂O—CHFCF₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 22

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CHF—CH₂O—CF₂CHF—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 23

This example was carried out in the same manner as in Example 1 exceptthat H—CF₂CH₂—CH₂O—CF₂CH₂—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 24

This example was carried out in the same manner as in Example 1 exceptthat H—CH₂CHF—CH₂O—CH₂CHF—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 25

This example was carried out in the same manner as in Example 1 exceptthat H—CH₂CH₂—CH₂O—CH₂CHF—H that is a fluorinated chain ether compoundwas used as the liquid medium which is hard to generate carbon dioxide.

Example 26

This example was carried out in the same manner as in Example 1 exceptthat CH₃CH₂CH₂CH₂CH₂CH₂—O—CH₂CH₂CH₂CH₂CH₃ that is a non-fluorinatedchain monoether compound was used as the liquid medium which is hard togenerate carbon dioxide.

Example 27

This example was carried out in the same manner as in Example 1 exceptthat CH₃CH₂CH₂CH₂CH₂—O—CH₂CH₂—O—CH₂CH₂CH₂CH₂CH₃ that is anon-fluorinated chain diether compound was used as the liquid mediumwhich is hard to generate carbon dioxide.

Example 28

This example was carried out in the same manner as in Example 1 exceptthat tetrahydrofuran that is a non-fluorinated five-membered cyclicmonoether compound was used as the liquid medium which is hard togenerate carbon dioxide.

Example 29

This example was carried out in the same manner as in Example 1 exceptthat tetrahydropyran that is a non-fluorinated six-membered cyclicmonoether compound was used as the liquid medium which is hard togenerate carbon dioxide.

Example 30

This example was carried out in the same manner as in Example 1 exceptthat 1,3-dioxolane that is a non-fluorinated five-membered cyclicdiether compound was used as the liquid medium which is hard to generatecarbon dioxide.

Example 31

This example was carried out in the same manner as in Example 1 exceptthat 1,4-dioxane that is a non-fluorinated six-membered cyclic diethercompound was used as the liquid medium which is hard to generate carbondioxide.

Example 32

Graphite having an average particle diameter of 30 μm as carbon material(a), silicon having an average particle diameter of 6 μm as metal (b),and crystalline silicon oxide (SiO₂) having an average particle diameterof 13 μm as metal oxide (c) silicon were weighed at a mass ratio of5:35:60 and were mixed by so-called mechanical milling for 24 hours toobtain an anode active material. Note that, in this anode activematerial, silicon that is metal (b) was dispersed in crystalline siliconoxide that is metal oxide (c). And, this example was carried out in thesame manner as in Example 1 except that this anode active material wasused.

Example 33

Graphite having an average particle diameter of 30 μm as carbon material(a), silicon having an average particle diameter of 6 μm as metal (b),and amorphous silicon oxide (SiO_(x), 0<x≦2) having an average particlediameter of 13 μm as metal oxide (c) silicon were weighed at a massratio of 5:35:60 and the mixed powder was to be an anode active materialwithout any particular special treatment. Note that, in this anodeactive material, silicon that is metal (b) was not dispersed inamorphous silicon oxide that is metal oxide (c). And, this example wascarried out in the same manner as in Example 1 except that this anodeactive material was used.

Example 34

An anode active material which contained carbon, silicon and amorphoussilicon oxide (SiO_(x), 0<x≦2) at a mass ratio of 5:35:60 was obtainedby a method equivalent to that disclosed in Patent Document 3. Notethat, in this anode active material, silicon that is metal (b) wasdispersed in amorphous silicon oxide that is metal oxide (c). And, thisexample was carried out in the same manner as in Example 1 except thatthis anode active material was used.

Example 35

This example was carried out in the same manner as in Example 1 exceptthat a polyvinylidene fluoride (PVDF, produced by KUREHA CORPORATION,trade name: KF polymer #1300) was used as the anode binder.

Examples 36 to 69

These examples were respectively carried out in the same manner as inExamples 1 to 34 except that a polyamide-imide (PAI, produced by TOYOBOCO., LTD., trade name: VYROMAX (registered trade mark) was used as theanode binder.

<Evaluation>

Tests for the secondary batteries produced were conducted in which theywere repeatedly charged and discharged within a voltage range of 2.5 Vto 4.1 V in a thermostatic oven which was kept at a temperature of 60°C. The test results were shown in Table 1. Here, “C50/C5(%)” in Table 1means (discharged capacity at the 50^(th) cycle)/(discharged capacity atthe 5^(th) cycle) (unit: %), which is a cycle retention ratio.

TABLE 1 liquid medium which is hard to generate carbon dioxide contentanode cycle retention ratio kind (vol %) binder C50/C5 (%) Ex. 1H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PI 91 Ex. 2 H—CF₂CF₂—CH₂O—CF₂CF₂—H 10 PI 72Ex. 3 H—CF₂CF₂—CH₂O—CF₂CF₂—H 15 PI 83 Ex. 4 H—CF₂CF₂—CH₂O—CF₂CF₂—H 50 PI91 Ex. 5 H—CF₂CF₂—CH₂O—CF₂CF₂—H 60 PI 92 Ex. 6 H—CF₂CF₂—CH₂O—CF₂CF₂—H 70PI 75 Ex. 7 H—CF₂CF₂—CH₂O—CF₂CF₂—H 75 PI 51 Comp. Ex. 1 — 0 PI 11 Comp.Ex. 2 H—CF₂CF₂—CH₂O—CF₂CF₂—H 5 PI 18 Comp. Ex. 3 H—CF₂CF₂—CH₂O—CF₂CF₂—H80 PI not detected Ex. 8 CH₂F—O—CH₂CH₃ 40 PI 75 Ex. 9 CH₂F—O—CH₂CH₂F 40PI 76 Ex. 10 CH₂F—CH₂—O—CH₂CH₃ 40 PI 77 Ex. 11 CH₂F—CH₂—O—CH₂CH₂F 40 PI73 Ex. 12 CH₂F—CH₂—O—CH₂CH₂—O—CH₂CH₃ 40 PI 80 Ex. 13H—CF₂CF₂—CH₂O—CHFCF₂—H 40 PI 88 Ex. 14 H—CF₂CF₂—CH₂O—CF₂CHF—H 40 PI 89Ex. 15 H—CF₂CF₂—CH₂O—CF₂CH₂—H 40 PI 83 Ex. 16 H—CF₂CF₂—CH₂O—CH₂CH₂—H 40PI 85 Ex. 17 H—CHFCF₂—CH₂O—CF₂CF₂—H 40 PI 88 Ex. 18H—CF₂CHF—CH₂O—CF₂CF₂—H 40 PI 88 Ex. 19 H—CH₂CF₂—CH₂O—CF₂CF₂—H 40 PI 83Ex. 20 H—CH₂CH₂—CH₂O—CF₂CF₂—H 40 PI 85 Ex. 21 H—CHFCF₂—CH₂O—CHFCF₂—H 40PI 83 Ex. 22 H—CF₂CHF—CH₂O—CF₂CHF—H 40 PI 85 Ex. 23H—CF₂CH₂—CH₂O—CF₂CH₂—H 40 PI 84 Ex. 24 H—CH₂CHF—CH₂O—CH₂CHF—H 40 PI 84Ex. 25 H—CH₂CH₂—CH₂O—CH₂CHF—H 40 PI 82 Ex. 26CH₃CH₂CH₂CH₂CH₂—O—CH₂CH₂CH₂CH₂CH₃ 40 PI 69 Ex. 27CH₃CH₂CH₂CH₂CH₂—O—CH₂CH₂—O—CH₂CH₂CH₂CH₂CH₃ 40 PI 62 Ex. 28tetrahydrofuran 40 PI 65 Ex. 29 tetrahydropyran 40 PI 68 Ex. 301,3-dioxolane 40 PI 73 Ex. 31 1,4-dioxane 40 PI 71 Ex. 32H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PI 43 Ex. 33 H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PI 52Ex. 34 H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PI 93

TABLE 2 liquid medium which is hard to generate carbon dioxide contentanode cycle retention ratio kind (vol %) binder C50/C5 (%) Ex. 35H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PVDF 49 Ex. 36 H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PAI90 Ex. 37 H—CF₂CF₂—CH₂O—CF₂CF₂—H 10 PAI 71 Ex. 38 H—CF₂CF₂—CH₂O—CF₂CF₂—H15 PAI 82 Ex. 39 H—CF₂CF₂—CH₂O—CF₂CF₂—H 50 PAI 92 Ex. 40H—CF₂CF₂—CH₂O—CF₂CF₂—H 60 PAI 92 Ex. 41 H—CF₂CF₂—CH₂O—CF₂CF₂—H 70 PAI 74Ex. 42 H—CF₂CF₂—CH₂O—CF₂CF₂—H 75 PAI 51 Ex. 43 CH₂F—O—CH₂CH₃ 40 PAI 76Ex. 44 CH₂F—O—CH₂CH₂F 40 PAI 74 Ex. 45 CH₂F—CH₂—O—CH₂CH₃ 40 PAI 77 Ex.46 CH₂F—CH₂—O—CH₂CH₂F 40 PAI 73 Ex. 47 CH₂F—CH₂—O—CH₂CH₂—O—CH₂CH₃ 40 PAI80 Ex. 48 H—CF₂CF₂—CH₂O—CHFCF₂—H 40 PAI 89 Ex. 49 H—CF₂CF₂—CH₂O—CF₂CHF—H40 PAI 89 Ex. 50 H—CF₂CF₂—CH₂O—CF₂CH₂—H 40 PAI 82 Ex. 51H—CF₂CF₂—CH₂O—CH₂CH₂—H 40 PAI 85 Ex. 52 H—CHFCF₂—CH₂O—CF₂CF₂—H 40 PAI 88Ex. 53 H—CF₂CHF—CH₂O—CF₂CF₂—H 40 PAI 90 Ex. 54 H—CH₂CF₂—CH₂O—CF₂CF₂—H 40PAI 83 Ex. 55 H—CH₂CH₂—CH₂O—CF₂CF₂—H 40 PAI 84 Ex. 56H—CHFCF₂—CH₂O—CHFCF₂—H 40 PAI 83 Ex. 57 H—CF₂CHF—CH₂O—CF₂CHF—H 40 PAI 85Ex. 58 H—CF₂CH₂—CH₂O—CF₂CH₂—H 40 PAI 83 Ex. 59 H—CH₂CHF—CH₂O—CH₂CHF—H 40PAI 84 Ex. 60 H—CH₂CH₂—CH₂O—CH₂CHF—H 40 PAI 82 Ex. 61CH₃CH₂CH₂CH₂CH₂—O—CH₂CH₂CH₂CH₂CH₃ 40 PAI 69 Ex. 62CH₃CH₂CH₂CH₂CH₂—O—CH₂CH₂—O—CH₂CH₂CH₂CH₂CH₃ 40 PAI 62 Ex. 63tetrahydrofuran 40 PAI 65 Ex. 64 tetrahydropyran 40 PAI 68 Ex. 651,3-dioxolane 40 PAI 73 Ex. 66 1,4-dioxane 40 PAI 71 Ex. 67H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PAI 40 Ex. 68 H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PAI 49Ex. 69 H—CF₂CF₂—CH₂O—CF₂CF₂—H 40 PAI 92

As shown in Tables 1 and 2, the cycle retention ratios of the secondarybatteries produced in Examples 1 to 69 were larger than the cycleretention ratios of secondary batteries produced in Comparative Examples1 to 3. It has been revealed from this result that capacitydeterioration of the secondary battery which is associated with acharge/discharge cycle at 45° C. or higher can be improved by anexemplary embodiment of the invention even when the anode activematerial of the electrode element is a silicon oxide.

(Additional Statement)

Some or all of the above-mentioned embodiments can also be described asthe following additional statements, but is not limited to thefollowing.

(Additional Statement 1)

A secondary battery, comprising an electrode element in which a cathodeand an anode are stacked, an electrolytic solution, and an outerpackaging body which encloses the electrode element and the electrolyticsolution inside;

wherein the anode is formed by binding an anode active material, whichcomprises carbon material (a) that can absorb and desorb a lithium ion,metal (b) that can be alloyed with lithium, and metal oxide (c) that canabsorb and desorb a lithium ion, to an anode collector with an anodebinder; and

wherein the electrolytic solution comprises a liquid medium which ishard to generate carbon dioxide at a concentration of 10 to 75 vol %.

(Additional Statement 2)

The secondary battery according to Additional statement 1, wherein theliquid medium which is hard to generate carbon dioxide does not have a—COO— group.

(Additional Statement 3)

The secondary battery according to Additional statement 2, wherein theliquid medium which is hard to generate the carbon dioxide is a chainether compound.

(Additional Statement 4)

The secondary battery according to Additional statement 3, wherein thechain ether compound is a fluorinated chain ether compound.

(Additional Statement 5)

The secondary battery according to Additional statement 4, wherein thefluorinated chain ether compound is represented by following formula(1):H—(CX¹X²—CX³X⁴)_(n)—CH₂O—CX⁵X⁶—CX⁷X⁸—H  (1).In formula (1), n is 1, 2, 3 or 4, and X¹ to X⁸ are each independently afluorine atom or a hydrogen atom. However, at least one of X¹ to X⁴ is afluorine atom, and at least one of X⁵ to X⁸ is a fluorine atom. Also, asfor the atom ratio of the fluorine atom and the hydrogen atom which arebonded to the compound of formula (1), [(the total number of thefluorine atom)/(the total number of the hydrogen atom)]≧1.(Additional Statement 6)

The secondary battery according to Additional statement 5, wherein thefluorinated chain ether compound is represented by following formula(2):H—(CF₂—CF₂)_(n)—CH₂O—CF₂—CF₂—H  (2).In formula (2), n is 1 or 2.(Additional Statement 7)

The secondary battery according to Additional statement 3, wherein thechain ether compound is a non-fluorinated chain ether compound.

(Additional Statement 8)

The secondary battery according to Additional statement 2, wherein theliquid medium which is hard to generate carbon dioxide is anon-fluorinated cyclic ether compound.

(Additional Statement 9)

The secondary battery according to any one of Additional statements 1 to8, wherein all or a part of metal oxide (c) has an amorphous structure.

(Additional Statement 10)

The secondary battery according to any one of Additional statements 1 to9, wherein metal oxide (c) is an oxide of a metal which constitutesmetal (b).

(Additional Statement 11)

The secondary battery according to any one of Additional statements 1 to10, wherein all or a part of metal (b) is dispersed in metal oxide (c).

(Additional Statement 12)

The secondary battery according to any one of Additional statements 1 to11, wherein metal (b) is silicon.

(Additional Statement 13)

The secondary battery according to any one of Additional statements 1 to12, wherein the anode binder is a polyimide or polyamide-imide.

(Additional Statement 14)

The secondary battery according to any one of Additional statements 1 to13, wherein the electrode element has a planar stacking structure.

(Additional Statement 15)

The secondary battery according to any one of Additional statements 1 to14, wherein the outer packaging body is an aluminum lamination film.

The present application claims the priorities based on Japanese PatentApplication No. 2009-224546, filed on Sep. 29, 2009, and Japanese PatentApplication No. 2010-196630, filed on Sep. 2, 2010, all the disclosureof which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

An exemplary embodiment of the invention can be utilized in everyindustrial field in need of a power supply and in an industrial fieldconcerning transportation, storage and supply of electrical energy.Specifically, it can be utilized, for examples, for a power supply of amobile device such as a mobile phone and a laptop computer; a powersupply of a moving or transport medium such as a train, a satellite anda submarine, and which includes an electric vehicle such as an electriccar, a hybrid car, an electric motorcycle and an electric power-assistedbicycle; a back-up power supply such as UPS; and a power storage deviceof electric power which is generated by a solar power generation or awind power generation.

EXPLANATION OF SYMBOL

-   a anode-   b separator-   c cathode-   d anode collector-   e cathode collector-   f cathode terminal-   g anode terminal

What is claimed is:
 1. A secondary battery, comprising an electrodeelement in which a cathode and an anode are oppositely disposed, anelectrolytic solution, and an outer packaging body which encloses theelectrode element and the electrolytic solution inside; wherein theanode is formed by binding an anode active material, which comprisescarbon material (a) that can absorb and desorb a lithium ion, silicon(b) that can be alloyed with lithium, and silicon oxide (c) that canabsorb and desorb a lithium ion, to an anode collector with an anodebinder, wherein the electrolytic solution comprises a fluorinated chainether compound, a cyclic carbonate and a chain carbonate, and whereinthe fluorinated chain ether compound is present at a concentration of 15to 60 vol % based on the total amount of the fluorinated chain ethercompound and the carbonates, wherein the anode binder comprisespolyimide or polyamide-imide; wherein all or a part of the siliconeoxide (c) has an amorphous structure and all or a part of the silicon(b) is dispersed in the silicon oxide (c); wherein the fluorinated chainether compound is represented by following formula (1);H—(CX¹X²—CX³X⁴)_(n)—CH₂O—CX⁵X⁶—CX⁷X⁸—H  (1) wherein in formula (1), n is1, 2, 3 or 4, and X¹ to X⁸ are each independently a fluorine atom or ahydrogen atom; and wherein the electrode element has a planar stackingstructure.
 2. The secondary battery according to claim 1, wherein informula (1), at least one of X¹ to X⁴ is a fluorine atom, and at leastone of X⁵ to X⁸ is a fluorine atom, and the atom ratio of the fluorineatom and the hydrogen atom which are bonded to the compound of formula(1) satisfies the following relation:[(the total number of the fluorine atom)/(the total number of thehydrogen atom)]≧1.
 3. The secondary battery according to claim 2,wherein the fluorinated chain ether compound is represented by followingformula (2):H—(CF₂—CF₂)_(n)—CH₂O—CF₂—CF₂—H  (2) wherein in formula (2), n is 1 or 2.4. The secondary battery according to claim 1, wherein the ratio ofcarbon material (a) is between 2 mass % and 30 mass % with respect tothe total amount of carbon material (a), silicon (b) and silicon oxide(c), the ratio of silicon (b) is between 20 mass % and 50 mass % withrespect to the total amount of carbon material (a), silicon (b) andsilicon oxide (c), and the ratio of silicon oxide (c) is between 40 mass% and 70 mass % with respect to the total amount of carbon material (a),silicon (b) and silicon oxide (c).
 5. The secondary battery according toclaim 1, wherein the anode binder comprises a polyamide-imide.
 6. Thesecondary battery according to claim 1, wherein in formula (1), at leastone of X¹ to X⁴ is a fluorine atom, and at least one of X⁵ to X⁸ is afluorine atom.